While composites are usually a fiber reinforced resin matrix that is rigid and incompressible in all dimensions, certain uses such as for automobile bumpers require some flexibility and shock absorbing capability, plus the ability to return to the original shape once an impact force is removed. Similarly, pads used in athletic shoes, floor carpets, carpet pads, gym floors etc. require the structures to have a high degree of both compressibility and resiliency so they can spring back to their original shape and size upon removal of an applied load.
In soles/heels for sports shoes, which are usually solid viscoelastomeric materials, some attempts to improve “cushioning” have been to mold in for example “air channels or pockets.” However, the rigidity of the molded material is such that cushioning effects are limited. In related art, U.S. Pat. No. 3,553,857 to Pettit describes a sole unit of elastomeric soling material other than thermoplastic rubber and carrying a dried film of a solvent-based polyurethane or polychloroprene adhesive superimposed on a halogenated surface of the sole unit.
U.S. Pat. No. 3,733,721 to Clemens describes a resilient pad, for example, foamed elastomeric material with the pad being generally contoured for mounting on the bottom of an article of footwear, such as a shoe, or the like. The pad is provided with pressure sensitive adhesive on the upper side so that it can be adhered to the bottom of an article of footwear to provide a cushion, while the pad can readily be removed from the articles of footwear when desired.
U.S. Pat. No. 4,608,768 to Cavanagh describes an athletic shoe having a shock-absorbing running sole which has at least one intermediate support extending at least approximately in parallel with a major plane of the running sole. The intermediate openwork support is disposed in a softly elastic midsole provided between an insole and a running sole.
U.S. Pat. No. 5,480,646 to Vu relates to a pad for applying medicaments, such as an insole worn in footwear, lined with a mixture of cinnamon, aloe wood and anise star powders having a pervious surface for contacting the skin and exposing the skin to emanations from the powders. The pad has a plurality of chambers which contain portions of the powder and maintain the even distribution of the powder as a lining in the pad. See also patents discussed in the background of the '646 patent.
These structures, however, lack the required through thickness compression and spring back property. Incorporating “elastic” (in the thickness or radial direction) media into soles has affected to some degree the resiliency or spring back of the soles once a normal load is removed. But again, using these media, the compressibility and spring back is limited to some portion of the media thickness at most.
Therefore, it would be an advancement in the state of the “pad-making” art to provide a pad that provides excellent elastic behavior under load with high through thickness recovery.